An implantable antenna, operating at the dual Industrial, Scientific, and Medical (ISM) bands of 902-928 MHz and 2.4-2.48 GHz, is presented for RF energy harvesting and data transmission. By introducing multiple radiating branches and etching a C-shaped slot, multiple resonant frequencies were generated to produce the wide dual bands. The proposed antenna has compact dimensions of 7.9 × 7.7 × 1.27 mm3. The simulated impedance bandwidths of the antenna are 0.67-1.05 GHz (44.2%) and 2.11-2.96 GHz (33.5%), and the peak gains are -28.9 dBi and -29.5 dBi, respectively. The lower band can be applied in RF energy harvesting, while the upper band is designed for data transmission with external medical equipment. Furthermore, to convert RF power into DC power, in RF energy harvesting, a voltage-doubled rectifier was positioned under the ground plane of the proposed antenna. The rectifier circuit can achieve a maximum conversion efficiency of 52% at an input power of 5 dBm. Furthermore, the integrated scheme of the implantable rectenna was fabricated and the numerical performance of the wireless power transfer was verified with the measurement results.
Keywords: RF energy harvesting; dual bands; implantable antenna; rectenna; rectifier; wide band; wireless power transfer.